Method and apparatus for preparing wires for threading perforated articles



Sept 8,` 1970 w. ROHRBACH 3,526,957

ES FOR THREADING METHOD AND APPARATUS FOR PREPARING WIR PERFORATED ARTICLES 2 Sheets-Sheet 1 Filed NOV. 28, 1.967

rm. @.Nlkl @zu mm.; mmnoo 321m mwoz 53.5@ @2:22

HIIIIIIVIH Sept. 8, 1970 w. RoHRBAcl-l 3,526,957

- METHOD ANDAPPARATUS FOR PREPARING WIRES FOR THREADING PERFORATED ARTICLES Filed Nov. 2e, 1967 2 sheet's4sneet a United States Patent() ABSTRACT OF THE DISCLOSURE A method, and apparatus for practicing the method, for preparing the ends of an array of wires for stringing through an array of computer memory cores is disclosed.

The wires are placed under tension, locally heated to reduce their tensile strength, and thereby broken. This method of preparation forms rounded wire ends which facilitate the threading of the wires through the cores.

BACKGROUND Many modern computers use an array of computer cores of magnetic material as their primary memory. These cores commonly take the form of toroids. Various wires which act as drive lines and sense lines must be inserted through the apertures or perforations of the toroidal cores before the computer memory will function. The present invention deals with the problem of inserting the wires through the array of cores.

Originally, wires were inserted through the array of cores by hand. This proved to be expensive and slow. Inserting the wires by hand is slow because only one wire can be inserted at a time and because great care has to be taken to avoid bending the soft copper wire. A bent wire impedes further progress of the wire through the array of cores.

Threading core arrays by machine was found to be cheaper, faster, and more accurate. It is cheaper and faster because many wires may be threaded simultaneously. It is more accurate because a machine can provide better alignment through the use of wire guides.

A problem still exists, however, because of the softness of the copperwire. Whether threaded by machine or by hand, the copper wire must be threaded through al1 cores without hitting a core edge which would bend the wire and stop its forward progress. A

Previous solutions tried include the techniques of: welding steel needles to the wire ends for' insertion; inserting metal tubes through the core arrays and threading the wires through the metal tubes; and vibrating the wires in an attempt to prevent them from catching on core edges. The steel needles provided the` longitudinal strength needed to prevent the wire from bending upon insertion, through the cores; however, welding process is slow and the needles are used mainly to insert the wires by handfUsing a tube has the immediate limitation of preventing the full utilization of the core aperture since the tube has a nite thickness. Using the full area is very important in building modern computer memories because it is highly desirable to use the largest wire size possible commensurate with the core opening. Vibrating the wire provides mechanical diiculties.

None of the previous methods solve the basic problem-how to prepare wire ends so as to avoid catching a core edge and stopping the progress of the wire through the core array-all of them merely avoid it. The present invention teaches a solution of the problem by teaching the end preparation of an array of wires so that rounded edges are formed. With rounded edges if the advancing 3,526,957 Patented Sept. 8, 1970 wire hits a core edge, it is pushed back towards the center of the core and is not stopped.

DESCRIPTION It is an object of the present invention to advance the art of threading wires through small diameter openings.

Further objects and advantages may be ascertained from an understanding of the description of the illustrative embodiment of the invention and from the appended claims.

The illustrative embodiment may best be described by reference to the accompanying drawings where:

FIG. l shows the top view of a machine for Stringing or threading wires through computer cores which uses the teachings of the present invention.

FIG. 2 shows a side view of the machine of FIG. l.

FIGS. 3 to 5 show magnied views of wire ends under various techniques of cutting including the technique taught =by the present invention.

In FIG. l a Wire supply 10 includes many spools of wire 12 feeding wire through Teflon tubes 14 for assembly by wire guides 16. The wires are then fed to a front wire guide 20, over a heating device 22, through a front clamp assembly 24, through an array of cores 26, and to a rear clamp assembly 28.

FIG. 2 shows a side view of the apparatus within FIG. l. A pneumatic device 30 for longitudinally moving a wire tension device 18 is shown `along with a second pneumatic device 32 within wire tension device 18. The second pneumatic device 32 applies a vertical clamping pressure on the array of wires thus enabling pneumatic device 30 to stretch or apply tension to the wires by moving wire tension device 18 with respect to either clamp assembly 24 or 28. A wire feeder 19 is seen to include rollers 34 which are manually or automatically driven 4to advance the wire. A third pneumatic device 36 acts as a means for moving heating device 22 proximate the array of wires in order to cause their tensile separation. The wire guides 23 associated with heating device 22 are more clearly seen. A table and stand 38 support the array of cores 26 and a vacuum box 29. Vacuum box 29 holds the individual cores of array 24 while the wires are threaded. In the preferred embodiment, the core array is held by a transfer plate as described in application No. 666,076 dated Sept. 7, 1967, and entitled Arrangement for Holding Magnetic Cores for Stringing by the present inventor and assigned to the present assignee. The transfer plates are then held by vacuum box 29. OPERATION Generally the apparatus of FIGS. 1 and 2 operates by rollers 34 pulling wire from spools 12, through Teon guides 14, through guides 16, and tension device 18. Rollers 34 also push the wire through front wire guides 20, through the core array, and to clamp 28. The wires are then clamped at the front and the back by clamps 24 and 28. Tension is next placed on the wire by: pneumatic device 32 extending to grip the wires in a vertical direction by pressure between the top of the housing of wire tension device 1'8 and wire guides 16; and pneumatic device 30 extending horizontally to stretch the wires between clamp 24 or 28 and wire tension device 18. At this point pneumatic device 36 extends to bring the preheated electrical heating device 22 proximate the array of wires. Pneumatic device 36 is shown extended in FIG. 2. The wires are heated by heating device 22 and broken as hereinafter explained more fully. The tension supplied by wire tension device 18 immediately withdraws the ends of the wires from heating device 22. This procedure is repeated until all Wires desired have been threaded.

Wire guides 23 prevent the fusion of adjacent wires upon heating. When pneumatic device 36 brings heating device 22 proximate the wires, guides 23 individually separated the wires since wire guides 23, 20, and .16 have identical spacing.

Wire guides 14, 16, and 20 form the wires from the individual spools 12 into an array which is configured to align with the apertures of the core array 26. That is, assuming the usual flat core array, wire guides 14, 16, and 20 form the wires from the various spools into a at horizontal array of wires.

By this heating under tension procedure, the ends of the wires next advanced by rollers 34 have the shape shown in FIG. 3. This smooth and tapered shape allows easy threading of the wires through the apertures within the cores since the wire ends do not readily catch on the core aperture edges. Also, if the wires are slightly misaligned and hit the aperture edges, the smooth and.

tapered shape of the Wire ends causes the wires to move back towards the aperture center and their forward progress is not stopped.

Other possible wire end shapes are shown in FIGS. 4 and 5. The shape shown in FIG. 4 is the result of cutting the wire end with a sharp knife. It is seen that this shape will readily catch on any edge available and stop the progress of an advancing wire. The shape shown in FIG. is the result of merely pulling the wire apart. This shape, while tapered with respect to the wire, will also catch on any edge available since the insulation separation is jagged.

Thus, it is seen that the formation of a smooth and tapered end is highly desirable, A smooth and tapered end is formed by placing tension upon the wire and locally heating the wire. Locally heating the wire locally reduces its tensile strength. Therefore, if the tension placed on the wire is greater than the local tensile strength at the point in the wire heated, the wire will break at this point. Notice, the wire breaks where desired. It does not break anywhere in the length under tension as would be true if tension alone were used to break the wire.

The additional advantage of using heat along with tension is seen by comparing FIGS. 3 and 5. Since the insulation melts with the application of heat, the insulation will tiow over the tapered end of the wire as it is pulled apart by the tension. Thus, the heating eliminates the problem of FIG. 5 where the insulation forms a jagged edge and can catch on edges of the cores.

The tension needed on the wire and the temperature to which the wire need be heated is dependent upon the type of wire used and the size of the wire used. One example will show the consideration involved and allow the extrapolation of the present technique to other wire sizes and types of wire.

Number 36 AWG cold rolled copper magnet wire with a synthetic iilm insulation of polyurethane and nylon has an average tensile strength of 40,000 pounds per square inch. If this wire is heated to a temperature near 600 Fahrenheit, the average tensile strength is reduced to 18,000 pounds per square inch-over a 50% reduction. The total reduction in tensile strength is due to the combination of two factors-the heating of the wire and the melting of the wire insulation. Copper, like most metals, shows a drop in its tensile strength when annealed or elevated to higher temperatures. In fact, heating the number 36 wire to near annealing temperatures produces a 30 to 35% drop in tensile strength. The remaining l5 to 20% drop in tensile strength is due to the melting of the wire insulation. The nylon and polyurethane insulation used in this embodiment has a melting temperature of 500 to 700 Fahrenheit and contributes l5 to of the tensile strength of the wire. So, heating the insulation to a temperature near 700 Fahrenheit melts it and removes its contribution to the wire tensile strength. Therefore, if the tension on the wire is slightly in excess of one-half of the original tensile strength, the

tension will be sufiicient to locally break the wire over heating device 22. So long as the tension on the wire is below its elastic limit, no significant resistance change will result. Any marked resistance change would detrimentally aiect the electrical characteristics and is not desired.

It will be obvious to those skilled in the art that many variations can be made within the teachings of the present invention. For example, in the embodiment explained, heating device 22 is an electrical resistance. This resistance may be activated by: both applying power to heat the resistance and positioning it adjacent the array of wires; allowing it to remain hot at all times and merely first moving it adjacent the wires and second moving it a signilicant distance away from the wires; and allowing it to remain adjacent to the array of wires and activating it by applying power at the proper time. Further, many methods of heating the wire will be envisioned; however, an electrical resistance is preferred.

Also, many, sizes and types of wire and insulation may be used following the teachings of the present invention.

The description of the present invention is for illustrative purposes only and is not intended as a limitation. Many alternates or variations will be obvious to one skilled in the art. It is desired that the present invention be limited only by the appended claims in which it is intended to cover the full scope and spirit of the present invention.

I claim: n

1. Apparatus for preparing a plurality of insulated wires for threading through an array of computer memory cores having at least one aperture per core, comprising 1n combination:

(a) means for providing a plurality of insulated wires configured to align with the apertures of the array of memory cores;

(b) a clamp for holding the wires in a lixed position;

(c) a tension device for applying a lonigtudinal tension to the wires with respect to the clamp;

(d) a heating device between the clamp and the tension device; and

(e) means for activating the heating device for causing the breaking of the wires and also for causing a tapered shape to be formed on the wire ends with insulation molded to the tapered wire ends;

whereby the wires are threaded through the array of cores, clamped, placed under tension, and locally heated to separate the wires in preparation for threading the next array.

2. The apparatus of claim 1, wherein the heating device comprises an electrical resistance.

3. The apparatus of claim 2, wherein the activating means comprises a device attached to the heating device for positioning the heating device immediately adjacent the array of wires for heating the wires and for positioning the heating device at a significant distance from the array of wire for allowing the movement of the array of wires past the heating device without heating the wires.

4. The apparatus of claim 3, wherein the activating means includes means for controlling the power supplied to the electrical resistance.

5. The apparatus of claim 2, wherein the activating means includes means for controlling the power supplied to the electrical resistance.

6. The apparatus of claim 1, wherein the activating means comprises a device attached to the heating device for positioning the heating device immediately adjacent the array of wires for heating the wires and for positioning the heating device at a signilicant distance from the array of wire for allowing the movement of the array of wires past the heating device without heating the wires.

7. A method of threading at least one wire through at least one perforated'object having a perforation diameter less than l0 tlmes the wire diameter where the wire is slowly advanced through the perforation in the object, held under tension, and cut in preparation for being threaded through at least one other object, wherein theimprovement comprises cutting the wire by locally heating the wire under tension to locally reduce the tensile strength of the wire, the heating and the tension locally cutting the wire and forming rounded ends on the Wire.

8. The method of claim 7, wherein the tension placed on the wire is at least one-half of the longitudinal tensile strength of the wire at room temperature.

9. An apparatus for simultaneously preparing a plurality of insulated wires for threading through an array of computer memory cores having at least one aperture per core, comprising in combination:

(a) means for aligning the wires in a general parallel arrangement;

(b) means for applying a predetermined tension to the wires; and

(c) means for applying heat adjacent and normal to the length dimension of the wires for causing the wire insulation to soften and the tensile strength of the wvire to be reduced below the magnitude of the applied tension.

10. An apparatus as claimed in claim 9, further comprising:

(a) means for selectively propagating the wires in a lengthwise direction through the aligning means; and

(b) means for selectively clamping the wire ends in a longitudinally-fixed position relative to the array of memory cores.

11. An apparatus as claimed in claim 10 wherein the aligning means is positioned proximate the array of computer memory cores and aligns the wires at a parallel spacing to allow the propagating means to insert adjacent wires into adjacent core apertures.

12. An apparatus as claimed in claim 9 wherein the means for applying heat further comprises:

(a) an electrical heating element; and

(b) means for controlling the displacement of the heating element relative to the plurality of wires to cause the heating element to be moved proximate the wires without making physical contact with the wires.

13. A method of end preparation of at least one insulated wire such that the wire may be easily threaded through at least one small diameter object, comprising the steps of:

(a) placing the wire under a longitudinal tension of at least one-half of the longitudinal tensile strength of the wire at room temperature;

(b) locally heating the wire for locally reducing the tensile strength of the Wire below the value of tension placed on the wire and causing the wire to break where it is heated, the heating and tensile break causing a tapered shape to be formed on the wire ends with the insulation molding to the wire ends.

References Cited UNITED STATES PATENTS 2,050,416 8/ 1936 Blanchard 72-342 X 2,066,876 1/ 1937 Carpenter 29-203 3,314,131 4/ 1967 Judge 29-203 3,435,518 4/1969 Denes 29-241 X 3,43 8,405 4/ 1969 Scheer 29-203 3,276,104 10/ 1966 Skogstad 29-604 3,226,805 1/ 1966 'Scott 29-631 3,461,532 8/1969 Lybarger 29-203 WAYNE A. MORSE, Primary Examiner U.S. Cl. X.R. 

